By the way, I’m not talking about the rage of the excluded and the dispossessed: Tea Partiers are relatively affluent, and nobody is angrier these days than the very, very rich. Wall Street has turned on Mr. Obama with a vengeance: last month Steve Schwarzman, the billionaire chairman of the Blackstone Group, the private equity giant, compared proposals to end tax loopholes for hedge fund managers with the Nazi invasion of Poland.

And powerful forces are promoting and exploiting this rage. Jane Mayer’s new article in The New Yorker about the superrich Koch brothers and their war against Mr. Obama has generated much-justified attention, but as Ms. Mayer herself points out, only the scale of their effort is new: billionaires like Richard Mellon Scaife waged a similar war against Bill Clinton.

Meanwhile, the right-wing media are replaying their greatest hits. In the 1990s, Mr. Limbaugh used innuendo to feed anti-Clinton mythology, notably the insinuation that Hillary Clinton was complicit in the death of Vince Foster. Now, as we’ve just seen, he’s doing his best to insinuate that Mr. Obama is a Muslim. Again, though, there’s an extra level of craziness this time around: Mr. Limbaugh is the same as he always was, but now seems tame compared with Glenn Beck.

Krugman is impressively accurate in his predictions. Here's what he now foresees:

So what will happen if, as expected, Republicans win control of the House? We already know part of the answer: Politico reports that they’re gearing up for a repeat performance of the 1990s, with a “wave of committee investigations” — several of them over supposed scandals that we already know are completely phony. We can expect the G.O.P. to play chicken over the federal budget, too; I’d put even odds on a 1995-type government shutdown sometime over the next couple of years.

It will be an ugly scene, and it will be dangerous, too. The 1990s were a time of peace and prosperity; this is a time of neither. In particular, we’re still suffering the after-effects of the worst economic crisis since the 1930s, and we can’t afford to have a federal government paralyzed by an opposition with no interest in helping the president govern. But that’s what we’re likely to get.

If I were President Obama, I’d be doing all I could to head off this prospect, offering some major new initiatives on the economic front in particular, if only to shake up the political dynamic. But my guess is that the president will continue to play it safe, all the way into catastrophe.